I have an AsRock Z97 (Haswell) ,i5 4690K, and RX 580. If I try to install Big Sur using Clover it goes to about 14min. left then an error occurs. What worked for me was to install Big Sur with OC and after the installation is completed I just replace the EFI folder (OC) with a Clover one that works for Mojave Catalina, and now Big Sur too. Perhaps this may help someone trying to install BS on a Haswell. If anyone comes across on how to fix the Haswell Clover Big Sur installation problem(s) please share it.